1. Instance property was renamed to the Current property

2. Now you can implement your own version of the `JsEngineSwitcher` class

Author: Taritsyn

NuGet/JavaScriptEngineSwitcher.Core/JavaScriptEngineSwitcher.Core.nuspec

@@ -12,7 +12,8 @@
 		<requireLicenseAcceptance>false</requireLicenseAcceptance>
 		<description>JavaScript Engine Switcher determines unified interface for access to the basic features of popular JavaScript engines (MSIE JavaScript Engine for .Net, Microsoft ClearScript.V8, Jurassic, Jint and ChakraCore). This library allows you to quickly and easily switch to using of another JavaScript engine.</description>
 		<summary>JavaScript Engine Switcher determines unified interface for access to the basic features of popular JavaScript engines (MSIE JavaScript Engine for .Net, Microsoft ClearScript.V8, Jurassic, Jint and ChakraCore).</summary>
-		<releaseNotes>In `IJsEngine` interface was added `SupportsScriptInterruption` property and `Interrupt` method.</releaseNotes>
+		<releaseNotes>1. `Instance` property was renamed to the `Current` property;
+2. Now you can implement your own version of the `JsEngineSwitcher` class.</releaseNotes>
 		<copyright>Copyright (c) 2013-2017 Andrey Taritsyn - http://www.taritsyn.ru</copyright>
 		<language>en-US</language>
 		<tags>JavaScriptEngineSwitcher JavaScript ECMAScript</tags>

NuGet/JavaScriptEngineSwitcher.Core/readme.txt

@@ -19,8 +19,8 @@
    =============
    RELEASE NOTES
    =============
-   In `IJsEngine` interface was added `SupportsScriptInterruption` property and
-   `Interrupt` method.
+   1. `Instance` property was renamed to the `Current` property;
+   2. Now you can implement your own version of the `JsEngineSwitcher` class.
 
    =============
    DOCUMENTATION

samples/JavaScriptEngineSwitcher.Sample.AspNet4.Mvc4/App_Start/JsEngineSwitcherConfig.cs

@@ -10,7 +10,7 @@ namespace JavaScriptEngineSwitcher.Sample.AspNet4.Mvc4
 {
 	public class JsEngineSwitcherConfig
 	{
-		public static void Configure(JsEngineSwitcher engineSwitcher)
+		public static void Configure(IJsEngineSwitcher engineSwitcher)
 		{
 			engineSwitcher.EngineFactories
 				.AddChakraCore()

samples/JavaScriptEngineSwitcher.Sample.AspNet4.Mvc4/Global.asax.cs

@@ -14,7 +14,7 @@ protected void Application_Start()
 
 			FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
 			RouteConfig.RegisterRoutes(RouteTable.Routes);
-			JsEngineSwitcherConfig.Configure(JsEngineSwitcher.Instance);
+			JsEngineSwitcherConfig.Configure(JsEngineSwitcher.Current);
 		}
 	}
 }

samples/JavaScriptEngineSwitcher.Sample.Logic/Services/JsEvaluationService.cs

@@ -18,7 +18,7 @@ public class JsEvaluationService
 	{
 		private static readonly Dictionary<string, string> _engineDisplayNameMappings;
 
-		private readonly JsEngineSwitcher _engineSwitcher;
+		private readonly IJsEngineSwitcher _engineSwitcher;
 
 
 		static JsEvaluationService()
@@ -35,11 +35,11 @@ static JsEvaluationService()
 
 #if NET40
 		public JsEvaluationService()
-			: this(JsEngineSwitcher.Instance)
+			: this(JsEngineSwitcher.Current)
 		{ }
 
 #endif
-		public JsEvaluationService(JsEngineSwitcher engineSwitcher)
+		public JsEvaluationService(IJsEngineSwitcher engineSwitcher)
 		{
 			_engineSwitcher = engineSwitcher;
 		}

src/JavaScriptEngineSwitcher.Core.Net4/JavaScriptEngineSwitcher.Core.Net40.csproj

@@ -59,6 +59,9 @@
     <Compile Include="..\JavaScriptEngineSwitcher.Core\IJsEngineFactory.cs">
       <Link>IJsEngineFactory.cs</Link>
     </Compile>
+    <Compile Include="..\JavaScriptEngineSwitcher.Core\IJsEngineSwitcher.cs">
+      <Link>IJsEngineSwitcher.cs</Link>
+    </Compile>
     <Compile Include="..\JavaScriptEngineSwitcher.Core\InterlockedStatedFlag.cs">
       <Link>InterlockedStatedFlag.cs</Link>
     </Compile>

src/JavaScriptEngineSwitcher.Core/IJsEngineSwitcher.cs

@@ -0,0 +1,39 @@
+namespace JavaScriptEngineSwitcher.Core
+{
+	/// <summary>
+	/// Defines a interface of JS engine switcher
+	/// </summary>
+	public interface IJsEngineSwitcher
+	{
+		/// <summary>
+		/// Gets or sets a name of default JS engine
+		/// </summary>
+		string DefaultEngineName
+		{
+			get;
+			set;
+		}
+
+		/// <summary>
+		/// Gets a collection of JS engine factories
+		/// </summary>
+		JsEngineFactoryCollection EngineFactories
+		{
+			get;
+		}
+
+
+		/// <summary>
+		/// Creates a instance of JS engine
+		/// </summary>
+		/// <param name="name">JS engine name</param>
+		/// <returns>JS engine</returns>
+		IJsEngine CreateEngine(string name);
+
+		/// <summary>
+		/// Creates a instance of default JS engine
+		/// </summary>
+		/// <returns>JS engine</returns>
+		IJsEngine CreateDefaultEngine();
+	}
+}

src/JavaScriptEngineSwitcher.Core/JsEngineSwitcher.cs

@@ -7,20 +7,41 @@ namespace JavaScriptEngineSwitcher.Core
 	/// <summary>
 	/// JS engine switcher
 	/// </summary>
-	public sealed class JsEngineSwitcher
+	public sealed class JsEngineSwitcher : IJsEngineSwitcher
 	{
 		/// <summary>
-		/// Instance of JS engine switcher
+		/// Default instance of JS engine switcher
 		/// </summary>
-		private static readonly Lazy<JsEngineSwitcher> _instance =
-			new Lazy<JsEngineSwitcher>(() => new JsEngineSwitcher());
+		private static readonly Lazy<IJsEngineSwitcher> _default
+			= new Lazy<IJsEngineSwitcher>(() => new JsEngineSwitcher());
+
+		/// <summary>
+		/// Current instance of JS engine switcher
+		/// </summary>
+		private static IJsEngineSwitcher _current;
+
+		/// <summary>
+		/// Gets or sets a instance of JS engine switcher
+		/// </summary>
+		public static IJsEngineSwitcher Current
+		{
+			get
+			{
+				return _current ?? _default.Value;
+			}
+			set
+			{
+				_current = value;
+			}
+		}
 
 		/// <summary>
 		/// Gets a instance of JS engine switcher
 		/// </summary>
-		public static JsEngineSwitcher Instance
+		[Obsolete("Use a `Current` property")]
+		public static IJsEngineSwitcher Instance
 		{
-			get { return _instance.Value; }
+			get { return Current; }
 		}
 
 		/// <summary>
@@ -43,12 +64,26 @@ public JsEngineFactoryCollection EngineFactories
 
 
 		/// <summary>
-		/// Private constructor for implementation Singleton pattern
+		/// Constructs an instance of JS engine switcher
+		/// </summary>
+		public JsEngineSwitcher()
+			: this(new JsEngineFactoryCollection())
+		{ }
+
+		/// <summary>
+		/// Constructs an instance of JS engine switcher
+		/// </summary>
+		public JsEngineSwitcher(JsEngineFactoryCollection engineFactories)
+			: this(engineFactories, string.Empty)
+		{ }
+
+		/// <summary>
+		/// Constructs an instance of JS engine switcher
 		/// </summary>
-		private JsEngineSwitcher()
+		public JsEngineSwitcher(JsEngineFactoryCollection engineFactories, string defaultEngineName)
 		{
-			DefaultEngineName = string.Empty;
-			EngineFactories = new JsEngineFactoryCollection();
+			EngineFactories = engineFactories;
+			DefaultEngineName = defaultEngineName;
 		}
 
 

src/JavaScriptEngineSwitcher.Extensions.MsDependencyInjection/JsEngineSwitcherServiceCollectionExtensions.cs

@@ -23,7 +23,7 @@ public static JsEngineFactoryCollection AddJsEngineSwitcher(this IServiceCollect
 				throw new ArgumentNullException("services");
 			}
 
-			JsEngineSwitcher engineSwitcher = JsEngineSwitcher.Instance;
+			IJsEngineSwitcher engineSwitcher = JsEngineSwitcher.Current;
 			services.AddSingleton(engineSwitcher);
 
 			return engineSwitcher.EngineFactories;
@@ -33,10 +33,10 @@ public static JsEngineFactoryCollection AddJsEngineSwitcher(this IServiceCollect
 		/// Adds a JS engine switcher to <see cref="IServiceCollection"/>
 		/// </summary>
 		/// <param name="services">The services available in the application</param>
-		/// <param name="configure">The <see cref="JsEngineSwitcher"/> which need to be configured</param>
+		/// <param name="configure">The <see cref="IJsEngineSwitcher"/> which need to be configured</param>
 		/// <returns>Instance of <see cref="JsEngineFactoryCollection" /></returns>
 		public static JsEngineFactoryCollection AddJsEngineSwitcher(this IServiceCollection services,
-			Action<JsEngineSwitcher> configure)
+			Action<IJsEngineSwitcher> configure)
 		{
 			if (services == null)
 			{
@@ -48,7 +48,7 @@ public static JsEngineFactoryCollection AddJsEngineSwitcher(this IServiceCollect
 				throw new ArgumentNullException("configure");
 			}
 
-			JsEngineSwitcher engineSwitcher = JsEngineSwitcher.Instance;
+			IJsEngineSwitcher engineSwitcher = JsEngineSwitcher.Current;
 			configure(engineSwitcher);
 
 			services.AddSingleton(engineSwitcher);

test/JavaScriptEngineSwitcher.Tests/JsEngineSwitcherInitializer.cs

@@ -19,7 +19,7 @@ public static void Initialize()
 		{
 			if (_initializedFlag.Set())
 			{
-				JsEngineSwitcher.Instance.EngineFactories
+				JsEngineSwitcher.Current.EngineFactories
 					.AddChakraCore()
 					.AddJint()
 					.AddMsie(new MsieSettings